@Wessj03
So if we take your firmware version of 1.6.4 and we use this chart https://community.tp-link.com/en/home/forum/topic/631936
We can see that your deco is currently on the 1.6.0 firmware platform based on your firmware of 1,6,x

If we use the chart again and look to see when VPN support was added it wasn't added till the platform that is right after yours which is 1.7.0 & 1.8.0

So it's definitely due to your deco not having new firmware. When will they get around to making new firmware for your unit? I have no idea. You could buy a newer model of deco but even that may get you VPN support. It will depend on which hardware version the model is and what firmware platform it's currently on.